1. Field of the Invention
The present invention relates to a process for manufacturing a ceramic element intended to be fitted onto a watch case, the visible surface of which includes features, and also to a ceramic element obtained by this process.
2. Description of Related Art
A process has already been proposed, in DE 2 533 524 and in EP 0 230 853, for depositing a metalized layer on a ceramic substrate that consists in depositing a CuO or Ti first layer with a thickness of at least 100 nm followed by a copper, silver, gold or nickel second layer. The adhesion between the two layers is obtained by passage through a furnace. In the case of copper and CuO, the temperature of the furnace must be between the CuO eutectic and the melting point of copper, i.e. between 1068° and 1078° C., which temperature is completely incompatible with the use of a photosensitive resin or photoresist, so that such processes do not allow the mask to be retained for the purpose of a subsequent electroforming operation.
Given that these processes do not allow the use of photosensitive materials, using techniques widely employed in the fabrication of electronic components in particular, it therefore cannot be used to actively grow features, such as digits, by electroforming since such masks would not withstand the temperature of the furnace treatment for bonding the layers.
Also proposed, in CH 636 238, is a process for forming symbols on watch parts made of an electrically non-conducting material, on which a metal layer, such as a Cr layer, is vacuum-deposited, this metal layer is covered with a photoresist in which apertures corresponding to the shape of the symbols have been formed, and a layer of a second metal, such as Au, Ni Rh, Va, is deposited electrochemically on the first metal layer through the apertures made in the layer of photoresist. Next, the resist is dissolved and then the first metal layer is chemically etched until the substrate reappears.
The main drawback of this approach stems from the fact that the chemical etching used to remove the first layer causes corrosion of the second layer. Furthermore, the deposition of the first layer by vacuum evaporation does not make it possible to achieve sufficient adhesion to form features on a watch case part, such as a watch bezel. This is because the abovementioned document proposes the formation of symbols on a watch case is protected by a watch glass, which is not the case with the bezel, which constitutes the most exposed part of the watch case. Symbols fitted onto a watch case bezel are therefore not protected, so that the process according to CH 636 238 does not allow symbols to be fixed onto a bezel with sufficient adhesion.
The object of the present invention is to remedy, at least partly, the abovementioned drawbacks.